JPH0627369U - Backup power supply circuit for vehicle electronic devices - Google Patents

Abstract

(57) [Abstract] [Purpose] To retain necessary data even when the battery is replaced, and to make the backup battery in the electronic device compact. [Structure] The input side of the backup stabilized power supply circuit 14 is connected to the vehicle battery 18, and the current limiting circuit 3 is connected to the output side.
Via 0, it is connected to the electronic circuit 32 and the reverse current prevention circuit 34 in which the data of the timepiece IC or the like may be lost. In addition, the output side of the reverse current prevention circuit 34 is connected to an auxiliary backup battery 42 made of a secondary battery, and an electronic circuit 40 in which data in the memory IC or the like is difficult to erase. Then, in the normal backup state, the vehicle battery 18 backs up the electronic circuits 32 and 40, and the battery 1
The battery 42 backs up the electronic circuit 40 when the 8 is replaced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a backup power supply circuit for an electronic device mounted on a vehicle such as a construction machine.

[0002]

[Prior art]

 In recent years, various electronic devices have been mounted on passenger cars, construction machines, and the like. These electronic devices have a volatile memory, an electronic timepiece, and the like, and in order to always operate the electronic device accurately, even if the engine of the vehicle is stopped, a predetermined electronic timepiece or memory is used. Electronic circuits need to be powered. Therefore, the vehicle electronic device is provided with a backup power supply circuit for backing up the electronic circuit. Then, conventionally, the method shown in FIGS. 3A and 3B has been adopted as a backup power supply circuit of a vehicle electronic device.

In FIG. 3A, the electronic device 10 is provided with two stabilized power supply circuits 12 and 14. One of the stabilized power supply circuits 12 operates the electronic device 10 when the engine is driven, and has an input side connected to the vehicle battery 18 via a key switch or a battery relay 16 and an output side reverse. It is connected to the input side of the current prevention circuit 20 and the load 22. The other stabilized power supply circuit 14 is for a backup power supply circuit, the input side is directly connected to the battery 18, and the output side together with the output side of the reverse current prevention circuit 20 requires an electronic circuit. It is connected to 24.

The backup power supply circuit configured as described above is provided in the electronic circuit 24 requiring backup when the engine is stopped, that is, when the key switch or the battery relay 16 is turned off. Electric power is supplied from the vehicle battery 18 via the digitalized power supply circuit 14. At this time, since the reverse current prevention circuit 20 is interposed between the load 22 and the stabilized power supply circuit 14, no current flows from the stabilized power supply circuit 14 to the load 22.

In the case of FIG. 3B, the electronic device 10 has one stabilizing power supply circuit 12, and this stabilizing power supply circuit 12 has a key switch or a battery relay 16 when the engine is driven as described above. It is connected to the battery 18 via and supplies electric power for operating the electronic device 10. The electronic circuit 26 requiring backup is connected to the reverse current prevention circuit 20 connected to the output side of the stabilized power supply circuit 12 and the backup battery 28 incorporated in the electronic device 10. Therefore, the electronic circuit 26 is backed up by receiving electric power from the battery 28 when the engine is stopped.

The backup power supply circuit shown in FIG. 3A is effective when the electronic circuit 24 requiring backup has a large power consumption, and when the battery 18 is replaced, the power is not supplied and the data is erased. It is also used as a backup for clock ICs that can operate even if it stops operating. On the other hand, the backup power supply circuit of FIG. 3B has a small power consumption and is used for backup of a memory IC or the like that needs to retain data even when the battery 18 is replaced.

[0007]

[Problems to be solved by the device]

 However, in recent years, the electronic devices installed in vehicles, including construction machinery, have become highly functional, and various electronic circuits such as those with large current consumption and those with inconvenience due to loss of data have been installed at the same time. You have a need to back up. Therefore, if the backup is performed by any of the methods shown in FIGS. 3A and 3B, the following inconvenience occurs.

If a backup as shown in FIG. 3 (A) is performed, necessary data in the memory will be erased when the in-vehicle battery 18 is replaced or the harness fails, and it is not easy to restore the data, and the data cannot be restored again. There is a risk of malfunction at startup. In addition, the backup of FIG. 3B has a problem that the battery 28 becomes larger and the number of times of replacement of the battery 28 increases as the backup current consumption increases due to the higher functionality of the electronic device.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and is a vehicle that can retain necessary data even when the battery is replaced and can reduce the size of the backup battery in the electronic device. The purpose is to provide a backup power supply circuit for electronic devices for automobiles.

[0010]

[Means for Solving the Problems]

 In order to achieve the above object, a backup power supply circuit for a vehicle electronic device according to the present invention is a secondary power supply circuit for a vehicle electronic device that supplies power to an electronic circuit from a vehicle battery when the engine is stopped. An auxiliary backup battery composed of a battery is connected to the electronic circuit in parallel with the vehicle battery, and the output voltage of the auxiliary backup battery is set lower than the power supply voltage of the battery to the electronic circuit. It has a feature.

[0011]

[Action]

 In the present invention configured as described above, the vehicle battery serving as the main backup power source and the secondary battery for the auxiliary backup are connected to the electronic circuit in which the data such as the volatile memory is not lost. Then, in the case of normal backup in which the vehicle engine is stopped, the electronic circuit is backed up by the output of the vehicle battery. In addition, when the electric power cannot be supplied from the battery to the electronic circuit, such as when replacing the battery, the electronic circuit is backed up by the auxiliary backup battery. Therefore, it is possible to retain data that should not be erased even when the vehicle battery is replaced. However, the auxiliary backup battery of the present invention is composed of a secondary battery, and the output voltage is lower than the power supply voltage to the electronic circuit of the vehicle battery. It's rechargeable, and a small battery provides effective backup.

[0012]

【Example】

 A preferred embodiment of a backup power supply circuit for a vehicle electronic device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of a backup power supply circuit of a vehicle electronic device according to an embodiment of the present invention.

In FIG. 1, the electronic device 10 is provided with stabilized power supply circuits 12 and 14. The stabilized power supply circuit 12 is for operating the electronic device 10 when an engine (not shown) of the vehicle is driven, and its input side is connected to the positive side of the vehicle battery 18 via a key switch or a battery relay 16. I am doing it. The output side of the stabilized power supply circuit 12 is connected to the input side of the reverse current prevention circuit 20 and the load 22.

On the other hand, the stabilized power supply circuit 14 is for backup of an electronic circuit described later, and is directly connected to the plus side of the vehicle battery 18 whose input side serves as a main backup power source. The output side of the stabilized power supply circuit 14 is connected to the electronic circuit 32 requiring backup and the input side of the reverse current prevention circuit 34 via a current limiting circuit 30 composed of a resistor or the like. Further, the output side of the reverse current prevention circuit 20 is connected to the input sides of the electronic circuit 32 and the reverse current prevention circuit 34, and when the engine is running, stabilization is performed via the reverse current prevention circuit 20. Power is also received from the power supply circuit 12 side. The electronic circuit 32 is composed of a timepiece IC or the like, which consumes a large amount of current, stops the supply of electric power when the battery 18 is replaced, and may lose data or stop operating.

The output side of the reverse current prevention circuit 34 is connected to one side of the resistor 36 and the cathode of the diode 38, and to the electronic circuit 40 in which data such as a memory IC that requires backup should not be erased. There is. The other side of the resistor 36 and the anode side of the diode 38 are connected to the positive side of the auxiliary backup battery 42. The battery 42 is composed of a secondary battery such as a nickel-cadmium battery and has an output voltage lower than the output voltage of the stabilized power supply circuits 12 and 14.

FIG. 2 shows a specific example of the reverse current prevention circuits 20 and 34. In FIG. 2A, the reverse current prevention circuits 20 and 34 are configured by diodes, and the anode is the input side and the cathode is the output side. That is, when the reverse current prevention circuit 34 is composed of a diode, the anode is connected to the current limiting circuit 30, the reverse current prevention circuit 20 and the electronic circuit 32, and the cathode is connected to the resistor 36, the cathode of the diode 38 and the electronic circuit 40. Connected.

FIG. 2B shows a specific example of the reverse current prevention circuits 20 and 34 using transistors. The reverse current prevention circuits 20 and 34 are composed of a Zener diode 44, a PNP type transistor 46, an NPN type transistor 48 and three resistors 50, 52 and 54. In the reverse current prevention circuits 20 and 34, the emitter of the transistor 46 is on the input side, the collector of the transistor 46 is on the output side, and the cathode of the Zener diode 44 is connected to the emitter of the transistor 46. There is. Further, the collector of the transistor 48 is connected to the base of the transistor 46 via the resistor 50. On the other hand, the anode of the Zener diode 44 is grounded via the resistors 52 and 54. The base of the transistor 48 is connected between the resistors 52 and 54, and the emitter is grounded.

In the case of the reverse current prevention circuits 20 and 34 of FIG. 2B, when the voltage applied to the cathode of the Zener diode 44 reaches the Zener voltage, a current flows in the Zener diode 44 from the cathode side to the anode side. Then, the transistor 48 is turned on by applying the Zener voltage divided by the resistors 52 and 54 to the base, and the amplified negative voltage is output to the collector to turn on the transistor 46. As a result, a current flows from the emitter side of the transistor 46 to the collector side. On the other hand, the transistor 46 is turned off when the voltage on the collector side is higher than that on the emitter side, and prevents current from flowing from the collector side to the emitter side.

The operation of the embodiment configured as described above is as follows. In the normal operation state of the electronic device 10, the key switch or the battery relay 16 is turned on to drive the vehicle engine, and the stabilized power supply circuit 12 is connected to the vehicle battery 18 via the key switch or the battery relay 16. . Then, the stabilized power supply circuit 12 stabilizes the output voltage of the battery 18 and gives it to the load 22, and through the reverse current prevention circuit 20, an electronic circuit 32 with large power consumption such as a timepiece IC, and a reverse current prevention circuit. 20. A reverse current prevention circuit 34 is applied to a low power consumption electronic circuit 40 such as a memory IC.

On the other hand, the stabilized power supply circuit 14 stabilizes the output voltage of the battery 18 similarly to the stabilized power supply circuit 12 and supplies the stabilized output voltage to the electronic circuit 32 via the current limit circuit 30. It is given to the electronic circuit 40 via the current prevention circuit 34. However, the current supplied from the stabilized power supply circuit 14 is limited by the current limiting circuit 30 to the maximum backup current of the electronic circuits 32 and 40 or less, and normally the current is not supplied to the maximum backup current or more. Then, the auxiliary backup battery 42 during the normal operation of the electronic device 10 is charged by the current passing through the reverse current prevention circuit 34 flowing through the resistor 36.

That is, the electronic circuit 40 includes a memory IC and the like, and the backup voltage is lower than the operating voltage. Since the output voltage of the auxiliary backup battery 42 configured by the secondary battery satisfies the backup voltage of the electronic circuit 40 and is set to a value lower than the operating voltage, the output voltages of the stabilized power supply circuits 12 and 14 are set. A voltage lower than the output voltage is applied to charge the battery.

When the engine of the vehicle is stopped, the key switch or the battery relay 16 is turned off, and the vehicle battery 18 backs up the electronic circuits 32 and 40. That is, the output of the battery 18 has its voltage stabilized by the stabilized power supply circuit 14, is supplied to the electronic circuit 32 through the current limiting circuit 30, and is also supplied to the electronic circuit 40 through the reverse current prevention circuit 34. Then, the battery 42 is charged in the same manner as above even in the normal backup state of the vehicle battery 18. However, since the reverse current prevention circuit 20 is provided between the current limiting circuit 30 and the load 22 so that the current does not flow from the current limiting circuit 30 side to the load 22 side, the load 22 does not receive power. Will never be supplied.

When the vehicle battery 18 is replaced or a harness (not shown) is broken, the electronic circuit 32 is not backed up by the battery 18, and thus the operation is stopped. Then, the auxiliary backup battery 42 supplies a current to the electronic circuit 40 via the diode 38 to back up the electronic circuit 40. At this time, since the reverse current prevention circuit 34 is provided between the electronic circuit 32 and the battery 42, the current from the battery 42 does not flow to the electronic circuit 32 side.

As described above, in the embodiment, in the case of normal backup, the vehicle battery 18 backs up the electronic circuits 32 and 40 and the auxiliary backup battery 42 is charged. Since the electronic circuit 40 is backed up only when the battery 18 is replaced or when the harness is broken, the battery 42 built in the electronic device 10 can be downsized. Moreover, the electronic circuit 40, which is troublesome if data such as a memory IC is lost, is backed up by the vehicle battery 18 and the auxiliary backup battery 42, so that necessary data can be retained even when the battery 18 is replaced. Then, in the embodiment, the stabilizing power supply circuit 12 for normal operation of the electronic device 10 and the stabilizing power supply circuit 14 for backup are provided side by side, and the current limiting circuit 30 is connected to the stabilizing power supply circuit 14 for backup. As a result, it is possible to reduce the power consumption of the backup power supply during the normal operation of the electronic device 10 and reduce the unnecessary current other than that consumed by the electronic circuits 32 and 40 during the backup.

In addition, in the above-described embodiment, the case where the invention is applied to the construction machine has been described, but the invention can also be applied to a normal passenger car or an electric vehicle. Further, the reverse current prevention circuits 20 and 34 are not limited to those shown in FIG.

[0026]

As described above, according to the present invention, the vehicle battery serving as the main backup power source and the secondary battery for the auxiliary backup are connected to the electronic circuit in which the data in the volatile memory is not lost. As a result, in the case of a normal backup when the vehicle engine is stopped, the electronic circuit is backed up by the output of the battery, and when it is not possible to supply electric power from the vehicle battery to the electronic circuit, such as when replacing the battery, Since the electronic circuit is backed up by the auxiliary backup battery, it is possible to retain data that cannot be erased even when the battery is replaced or the harness is broken. Moreover, since the auxiliary backup battery of the present invention is composed of a secondary battery and the output voltage is lower than the voltage applied to the electronic circuit of the vehicle battery, it is charged by the vehicle battery even in the normal backup state. The backup battery built into the electronic device can be made smaller.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a backup power supply circuit of an electronic device for a vehicle according to an embodiment of the present invention.

2A and 2B are circuit diagrams showing a specific example of a reverse current prevention circuit according to an embodiment, FIG. 2A is a circuit diagram of a reverse current prevention circuit using a diode, and FIG. 2B is a reverse current prevention circuit using a transistor. It is a circuit diagram of a circuit.

3A and 3B are explanatory views of a conventional backup power supply circuit, in which FIG. 3A is an explanatory view of a backup power supply circuit using a vehicle battery, and FIG. 3B is an explanatory view of a backup power supply circuit using a battery incorporated in an electronic device.

[Explanation of symbols]

 10 Electronic Device 12, 14 Stabilized Power Supply Circuit 18 Vehicle Battery 30 Current Limiting Circuit 32, 40 Electronic Circuit 42 Auxiliary Backup Battery

Claims (1)

[Scope of utility model registration request] 1. A backup power supply circuit for a vehicle electronic device that supplies electric power from a vehicle battery to an electronic circuit when an engine is stopped, and an auxiliary backup battery composed of a secondary battery is connected to the electronic circuit in parallel with the vehicle battery. In addition, the output voltage of the auxiliary backup battery is set to be lower than the power supply voltage to the electronic circuit by the battery, and the backup power supply circuit of the vehicle electronic device.